Computer networks are widely used to provide increased computing power, sharing of resources and communication between users. Computer systems and computer system components are interconnected to form a network. Networks may include a number of computer devices within a room, building or site that are interconnected by a high speed local data link such as local area network (LAN), token ring, Ethernet, or the like. Local networks in different locations may be interconnected by techniques such as packet switching, microwave links and satellite links to form a world-wide network. A network may include several hundred or more interconnected devices.
In computer networks, a number of issues arise, including traffic overload on parts of the network, optimum placement of network resources, security, isolation of network faults, and the like. These issues become more complex and difficult as networks become larger and more complex. For example, if a network device is not sending messages, it may be difficult to determine whether the fault is in the network device itself, the data communication link or an intermediate network device between the sending and receiving network devices.
Network management systems have been utilized in the past in attempts to address such issues. Prior art network management systems typically operated by remote access to and monitoring of information from network devices. The network management system collected large volumes of information which required evaluation by a network administrator. Prior art network management systems place a tremendous burden on the network administrator. He must be a networking expert in order to understand the implications of a change in a network device parameter. The administrator must also understand the topology of each section of the network in order to understand what may have caused the change. In addition, the administrator must sift through reams of information and false alarms in order to determine the cause of a problem.
It is therefore desirable to provide a network management system which can systematize the knowledge of the networking expert such that common problems can be detected, isolated and repaired, either automatically or with the involvement of less skilled personnel. Such a system must have certain characteristics in order to achieve this goal. The system must have a complete and precise representation of the network and the networking technologies involved. It is insufficient to extend prior art network management systems to include connections between devices. A network is much more than the devices and the wires which connect them. The network involves the network devices, the network protocols and the software running on the devices. Without consideration of these aspects of the network, a model is incomplete. A system must be flexible and extendable. It must allow not only for the modeling of new devices, but must allow for the modeling of new technologies, media applications and protocol. The system must provide a facility for efficiently encapsulating the expert's knowledge into the system.
It is a general object of the present invention to provide improved methods and apparatus for managing networks.
It is another object of the present invention to provide network management systems which utilize models of network entities and interrelationships between network entities.
It is a further object of the present invention to provide methods and apparatus for inferring information about network entities with which communication is impossible or impractical.
It is a further object of the present invention to provide methods and apparatus for determining the operational status of network devices, such as connectors, cables, buses, and the like, that are not capable of communication.